1.Shanghai Ecological Forecasting and Remote Sensing Center;2.Baoshan Meteorological Service;3.Meteorological Observation Center of CMA,China Meteorological Administration;4.Shanghai Meteorological Information and Technology Support Centre;5.Shanghai by Weather Technology Co., Ltd.
National Key R&D Program of China（2017YFC1501902,2017YFC1501701），The National Natural Science Foundation of China（41905007）；Shanghai Sailing Program（20YF1443400）
本文基于上海超大城市试验期间宝山国家基本气象站部署毫米波云雷达在2019年的观测数据,辅以激光雨滴谱、微雨雷达、探空资料、风云四号卫星产品、地面雨量计等多源观测数据,从探测稳定性、探测能力、基数据和产品数据探测合理性等方面开展了毫米波云雷达观测质量评估。结果表明：毫米波云雷达在试验期间仅出现单次软件故障,且基数据全年获取率高于95%,探测稳定性较好；毫米波云雷达各高度最小可测回波强度位于-40至-20 dBZ区间,并随高度呈现出与理论相符的指数递减；9 km高度以下最小回波强度变化小于2 dB,最小回波探测能力稳定性较高,在降水率达到4-5 mm/h时,毫米波云雷达会出现强衰减导致的虚假晴空区。虽然多部毫米波云雷达的基数据存在差异,但与地面雨滴谱计算回波强度和微型雨雷达观测回波强度具有一致的垂直分布及时间演变特征。毫米波云雷达探测云顶云底高度与探空资料估算云顶云底高度、风云四号卫星反演云顶高度具有一定的一致性。拼接缝和距离旁瓣虚假回波是较为直观且能够对业务化应用产生直接影响的问题。本文末从上海气象自身发展需求出发,从业务化应用的角度对当前毫米波云雷达提出了改进建议。
The observational stability, observational ability, and rationality of both base data and products of millimeter cloud radar (MCR for short) installed at Shanghai Meteorological Service during “The study and experiment of vertical integrated meteorological observation technology in mega-cities” (MCME for short) have been evaluated using observations from ground-based Lidar distrometer, micro-rain radar, radiosonde, FY-4A’s products as well as surface rain gage. The results show that: the observational stability of MCR is considerably high that only one-time software failure happened during the MCME and the data acquisition rate is larger than 95%. The minimal detectable reflectivity of MCR is generally distributed within -40 to -20 dBZ and has an exponential distribution in the vertical direction which fits well with the theory. The minimal detectable reflectivity of MCR changes little (smaller than 2 dB for heights lower than 9 km) during the MCME. A false “No Cloud” region will be seen in the MCR’s observation when the rain rate is larger than 4-5 mm/h. Although the raw data of the two MCRs have certain differences, the pattern of reflectivity in the time-height cross-section is highly reasonable indicated by the comparisons between the reflectivity from MCR’s observation, the reflectivity calculated with Lidar distrometer’s observation, and the reflectivity from micro-rain radar’s observation. The cloud top height and cloud base height retrieved by MCR are also evaluated by the cloud top/base height calculated by radiosonde and cloud top height retrieved by FY-4A satellite, and the results show certainly a degree of consistency among the three observations. The inconsistency of reflectivity due to the merge of multiple pulses with different pulse widths used in MCR’s base data processing and the false “clear sky area” due to the strong attenuation are two obvious issues that may have significant impacts on the operational usage of MCR. The advice on how to improve the current MCR from the perspective of the demand for the development of the Shanghai Meteorological Service has been given at the end of the paper.
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